1. Field of the Invention
The present invention relates to an introduction device comprising an operation input unit which returns into a range including a predetermined neutral position when a hand is taken off in the middle of operation.
2. Description of the Related Art
As an introduction device, a medical or industrial endoscopic device to insert an elongate and flexible insertion portion which is provided with a curving portion at the distal end has been typically utilized for visual observation in a body cavity or in a conduit having curved parts. For example, when the medical endoscopic device is used for a diagnosis or surgery in the body cavity, the inside of the body cavity is observed while an operation portion comprising two operation dials is operated to curve the curving portion provided on the distal side of the insertion portion in an up-down (UD) direction and a right-left (RL) direction.
If the curving portion is electrically operated, the degree of curving the curving portion relative to the rotation angles of the operation dials can be freely set. That is, if a lower ratio of the curving angle at which the curving portion is curved to the rotation angles of the operation dials is set, it will be easier for an operator to more finely and slowly curve the curving portion. If the operation dials are configured to perform multi-rotation operation for one or more rotations (360 degrees or more) so that the curving portion can curve more slowly and finely, the operator operates the curving portion while repeatedly rotating the operation dials clockwise and counterclockwise. In this instance, it is difficult for the operator to recognize the curving state of the curving portion from the current rotational positions of the operation dials. For example, in the case of an operation dial capable of one and a half rotations (450 degrees), it may be difficult to recognize whether the current rotational position is 60 degrees or 420 degrees. When the operator cannot recognize the angle, the operator once stops the observation, returns the operation dials to a neutral position (e.g. scale 0) while looking at the operation dials at hand, and then again performs the curving operation.
For example, Jpn. Pat. Appln. KOKAI Publication No. 2009-219822 has suggested an endoscopic device which curves a curving potion by driving a motor. The curving potion of this endoscopic device is provided with a neutral return mechanism in which two spiral springs that are wound in opposite directions with respect to the rotation axis of an operation dial are arranged to face each other to return the operation dial to a neutral position. This neutral return mechanism is adjusted so that when the operation dial is rotated, one of the spiral springs is compressed, and the other spiral spring is expanded, and urging force thereby works to return the operation dial to the initial position (neutral position) where the curving potion linearly extends.
In an endoscopic device suggested in International Publication No. WO2012/074013A1, an RL operation dial to electrically curve a curving potion in the RL direction is disposed under an operation portion. It is shown that this RL operation dial is rotated by, for example, the second finger of a hand grasping the operation portion.